CopyofAlumLab - Migdalia Berrio AP Chemistry Alum Lab...

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Migdalia Berrio 9/23/16 AP Chemistry Alum Lab Objectives: 1. To prepare aluminum sulfate dodecahydrate (alum) from a water solution that contains K+, Al 3+ and SO4 2-. Pre Lab Questions: 1. Alum is aluminum sulfate dodecahydrate, or KAl(SO ) ·12H O 2. Alum is a hydrated crystal because it contains water molecules bonded to the ions as part of the crystal structure. 3. Things that can dissolve in both acids and bases are said to be amphoteric 4. Al(OH)3 (s) + OH- (aq) → [Al(OH)4]- (aq) 5. Al(OH)3 (s) + 3 H+ (aq) → Al3+(aq) + 3 H2O (l) 6. 1.0 grams K (474.39 g/mol KAL(SO4)2 x 12H2O) / (39.10 g/mol K) = 12.13 grams of potassium alum. 12 grams can be made 7. 4.5g/12g*100=37.5% Materials: 1. 250 mL beaker 2. KOH solution 3. Aluminum foil 4. Filter Paper
5. Funnel 6. Distilled water 7. Hot plate 8. Ice bath 9. Ethanol 10. Crucible and Cover 11. Ring Stand 12. Bunsen Burner 13. Spatula Procedure: 1. Put on PPE PART I: DAY 1: 1. Weigh out about 0.50 grams of aluminum foil and record the actual mass in the data table. 2. Tear the foil into small pieces and place in a 250 mL beaker. 3. Slowly add 25 mL of a 3 M KOH solution. Allow the reaction to proceed until all of the foil is dissolved. 4. Remove any undissolved solids such as carbon particles by filtering the solution through filter paper and funnel while the solution is hot. Rinse the filter paper with a small amount of distilled water. 5. At this point the solution contains [Al(OH)4] - and K+ ions, along with excess OHions.

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